1. Field of the Invention
The present invention relates to a light emitting device.
2. Description of the Related Art
FIG. 17 is a perspective view showing one production process of a conventional LED light emitting device 200. FIG. 18 is a cross-sectional view showing the LED light emitting device 200. The LED light emitting device 200 includes a package 206 and a lead 205, as shown in FIG. 8. The package 206 includes space that opens upward and has a substantially inverted truncated cone shape. The lead 205 is made of a conductive material and is fixedly attached to the package 206. The lead 205 includes a lead middle portion 205b that is located in a substantially middle part of the light emitting device, and a lead terminal portion 205a that projects outward of the package 206. When the lead 205 and the package 206 are fixedly attached, the lead middle portion 205b that is a part of the lead 205 is exposed in the space in the packaged 206 that has a substantially inverted truncated cone shape. An LED chip 203 is mounted on the exposed lead middle portion 205b in the space of the package 206. In addition, the lead middle portion 205b penetrates and extends inside the package 206 as shown by a dashed line. The lead then projects from a substantially center on the side surface of the package 206 in the thickness direction. The thus-projecting lead 205 is bent at substantially right angle so as to extend along the side surface of the package, and is again bent at substantially right angle so as to turn a corner toward the bottom of the package 206 as shown in FIG. 18. A lead region that extends outside the package 206, in other words, a lead region that is bent so as to extend along the side and bottom surfaces of the package 206 is referred to as the lead terminal portion 205a. Note that FIG. 17 is the perspective view showing the LED light emitting device 200 prior to bending the lead terminal portion 205a. Additionally, sealing resin 202 is filled in the space that opens in the package 206.
In conventional production of the light emitting device 200, a plurality of patterns for light emitting devices are formed in a lead frame 110 made of a sheet of conductive material as shown in FIG. 4. Subsequently, the lead frame is subjected to production processes. The lead frame is cut and separated into individual patterns in a certain process. Thus, a plurality of light emitting devices are produced at a time. FIG. 17 shows the individual light emitting device 200 that is separated by cutting proper locations in the lead 205 that connects LED light emitting devices after the aforementioned production processes.
As shown in FIG. 18, the LED chip 203 is mounted on the lead middle portion 205b, and they are electrically conducted to each other. In addition, the lead terminal portion 205a that is bent toward the bottom surface side of the light emitting device 200 is installed on a mount body 201 with conductive patterns by solder or the like. This installation provides electrically connection between the LED chip 203 and the mount body 201 through the lead terminal portion 205a. However, in this construction, there are problems that require a process for bending the lead terminal portion so as to adjust its alignment along the side and bottom surfaces of the semiconductor light emitting device, reduce resistance of lead terminal portion due to the bent lead terminal portion, and make the LED light emitting device thick since the lead terminal portion is bent so as to extend the side and bottom surfaces thereof.
Furthermore, the lead terminal portion 205a requires a length enough to be bent to some extent. In addition, since the lead 205 is made of a conductive material such as copper and iron, silver or the like is plated to prevent oxidation. The thus-plated lead 205 has good wettability, and can be stably bonded to the mount body 201 with solder or the like. Generally, the lead frame 110 is plated as shown in FIG. 4. The patterns on the plated lead frame 110 are subjected to LED light emitting device processing. In other words, in a process after plating, proper locations of the leads 205 that connect the LED light emitting devices are cut, as a result, the connected LED light emitting devices are separated into individuals. Accordingly, a cut surface 205c that is produced by cutting the lead 205 is not plated. For this reason, this cut surface is prone to be oxidized to rust. Additionally, since the oxidized cut surface 205c has poor wettability, solder or the like crawls. As a result, there is a problem that causes insufficient adhesiveness between the oxidized cut surface 205c and the mount body 201. Additionally, in mass-production processes of a number of LED light emitting devices, the sharp cut surface 205c of the lead terminal portion that projects from the end surface of one LED light emitting device may damage other semiconductor light emitting devices. On the other hand, since the lead terminal portion 205a is long, the lead terminal portion may be bent at an undesired angle due to some shock, or may be cut off. Additionally, long lead terminal portions reduce the number of leads that are arranged in patterns in one sheet of lead frame, and thus cause poor efficiency and comparatively high cost.
Furthermore, as shown in FIG. 18, in the case where the lead terminal portion 205a that contacts the bottom surface of the LED light emitting device 200 and the mount body 201 are fixedly attached with solder or the like, a surface layer of the lead terminal portion 205a serves as a bonding surface. Accordingly, in order to stably fix them, as shown in FIG. 17, the lead terminal portion 205a should have a width W to some extent. In addition, if the lead terminal portion 205a is not bent so as to extend along the bottom surface of the package 206, the bottom surface of the package 206 and the top surface of the mount body 201 are not bonded in parallel. In this case, the LED light emitting device may be fixedly attached at an incline. As a result, there is a problem that the reach of light emitted from the LED light emitting device 200 is deviated.
In order to prevent this deviation of the reach, as shown in FIG. 18, a projection portion 206a is disposed on the bottom surface of the package 206, so that the bottom surface of this projection portion 206a and the mount body 201 are in stable contact with each other. Accordingly, it is necessary to accommodate the lead terminal portion 205a in a height h of the projection portion 206a on the bottom surface of the package. However, depending on the length, bent angle or bent location of lead terminal portion 205a, the lead terminal portion 205a pushes the package 206 upward. Thus, a gap may be produced between the package 206 and the mount body 201. As a result, the installation angle or installation location of the LED light emitting device 200 can be deviated. In addition, the lead terminal portion 205a may not completely align along the bottom surface of the package 206, as a result, there is a problem that the LED light emitting device 200 and the mount body 201 are not stably and mechanically or electrically coupled to each other. Additionally, since the lead terminal portion has a relatively large width W, the width of the cut surface 205c correspondingly becomes wider. This increases the defect due to the aforementioned cut surface of the lead terminal portion.
Moreover, FIG. 19 is a perspective view showing another LED light emitting device 300. FIG. 20 is a side view of the LED light emitting device 300 shown in FIG. 19. The lead terminal portions of the LED light emitting device 300 shown in FIG. 19 have a length shorter than the lead terminal portion 205a of the LED light emitting device shown in FIGS. 17 and 18, and additionally are not bent. In addition, the lead terminal portions 305a of the LED light emitting 300 horizontally project outward of a package 306 from the bottom surface of the package 306 as shown in FIGS. 19 and 20. Accordingly, in the case where the LED light emitting device 300 contacts the mount body 301, the lead terminal portion 305a contacts the mount body 301. In this case, they can be fixed by solder or the like. As a result, it is not necessary to bend the lead terminal portion 305a so as to turn a corner toward the bottom surface side of the package 306, in order to provide a contact region with the mount body 301.
However, a projection portion is formed in a substantially rectangular projection on the end surface of the lead terminal portion 305a, and has a cut surface that is produced when the lead terminal portion 305a is cut off from a lead frame. Since this projection portion has edged corners, these parts may damage other light emitting devices 300. On the other hand, the defect that the cut surface is oxidized in air is not still solved. See Japanese Patent Laid-Open Publication TOKUKAI No. 2005-33194.